This invention relates to electric machines such as electric power generators and electric motors, and in particular to a stator winding support structure for use with a superconducting rotor.
In order to generate current, an electric generator typically includes a rotor and a stator, each of which contains a winding. The rotor is conventionally arranged within the stator to define an air gap therebetween.
The stator conventionally includes a frame and a cylindrically-shaped core having magnetic teeth on its inner circumference. The teeth of the stator core form a plurality slots which receive the stator winding and therefore provide radial and tangential winding support. The teeth of the stator core also provide a grounding plane since the stator winding contacts the teeth. These teeth, however, are not desirable or needed when the rotor winding is formed by a superconducting winding that produces a very strong magnetic field. In the absence of the teeth, the stator winding is arranged within the magnetic field and thus produces both tangential and radial pulsating forces imposed on itself. While the tangential forces provide useful torque during normal operation, the radial forces produce an undesirable stator winding vibration.
Several attempts have been made in the past to produce a superconducting generator in the 10/20 MVA size. Only limited success has been achieved, however, to support and hold a stator winding against the strong magnetic field produced by the superconducting rotor. This limited success has resulted, for example, from a very complex helical armature or air gap windings requiring numerous complex spring and tie devices.
It would thus be beneficial to provide a support structure for a stator winding for use with a superconducting rotor which supports the air gap between the rotor and stator and which transmits the torque between the stator and rotor while preventing stator winding vibration. The support structure supports and holds the stator winding circumferentially and radially against the stator core. It would be further beneficial to provide the support structure with a minimum number of parts and a minimum amount of complexity and cost.
In accordance with an exemplary embodiment of the present invention, a winding support structure for use with a superconducting rotor comprises an inner support ring, an outer support ring arranged around an outer circumference of the inner support ring, first and second support blocks coupled to said outer support ring and a lamination coupled to the first and second support blocks. A slot is defined between the support blocks and between the outer support ring and the lamination to receive a portion of a winding. The inner ring is a solid ring and the outer ring is a split ring. The outer ring expands to produce a radially outward force against the support blocks when the inner ring is moved axially with respect to the outer ring. The winding support structure may also comprise another inner support ring and another outer support ring which is arranged around the outer circumference of the another inner support ring and is coupled to the lamination. A clearance space in the slot is filled with a RTV. The winding structure may also comprise a third support block coupled to the outer support ring to define another slot between the second and third support blocks to receive another portion of the winding. The winding support structure transmits torque and prevents stator winding vibration.
In accordance with another exemplary embodiment of the present invention, a method of forming a winding support structure for use with a superconducting rotor comprises providing a lamination, coupling first and second support blocks to the lamination, providing an inner support ring and an outer support ring around an outer circumference of the inner support ring, and coupling the lamination and the support blocks to the outer ring to define a slot between the support blocks and between the lamination and the outer ring to receive a portion of a winding. An RTV is applied into a clearance space in the slot. Wedges are respectively arranged between adjacent bars forming the winding prior to applying the RTV into the clearance space and then removed after applying the RTV into the clearance space. Additional RTV is applied in a space where the wedges are removed. Coupling the lamination and the support blocks to the outer support ring comprises pulling the winding to the outer support ring and tying the winding to the inner and outer support rings. Providing an inner support ring and an outer support ring comprises providing a solid ring and a split ring, respectively. The outer ring expands to produce a radially outward force against the support blocks when the inner ring is moved axially with respect to the outer ring. Another outer support ring can be provided around an outer circumference of another inner support ring and coupled to the lamination. A third support block may be coupled to the outer support ring to define another slot between the second and third support blocks to receive another portion of the winding. The method of forming the winding support is accomplished using a minimal number of parts and minimal construction cost.
In accordance with yet another exemplary embodiment of the present invention, an apparatus for use with a superconducting rotor comprises an inner support ring, an outer support ring arranged around an outer circumference of the inner support ring, first and second support blocks coupled to the outer support ring, a lamination coupled to the first and second support blocks, and a winding. A portion of the winding is arranged within a slot that is defined between the support blocks and between the outer ring and the lamination. The inner ring is a solid ring and the outer ring is a split ring. The outer ring expands to produce a radially outward force against the support blocks and the winding when the inner ring is moved axially with respect to the outer ring. A clearance space in the slot is filled with an RTV. The apparatus can further comprise another inner support ring and another outer support ring which is arranged around the another inner support ring and coupled to the lamination. The apparatus can further comprise a third support block coupled to the outer support ring to define another slot between the second and third support blocks and between the outer support ring and the lamination, another portion of the winding being arranged in the another slot.